AMEN to what Crittercall said!
and that IS definitely a rabbits nest. Please do as she said and put them back. Mom will take them back, despite the old wives tale that people think they wont.
Mom leaves during the day and comes back at night. Bunnies have a very large tummy at birth to tide them over during the day. I am a bunny rehabber and the sad thing is many of the bunnies I get have nothing wrong with them, other than someone found them and thought they were abandoned when they probably weren't.
People truly mean well in picking wild babies up, but in many cases they unknowingly do more harm. If you see a baby in the wild, AND they don't look injured, please try to leave them alone and at most, maybe cover them up a bit if they look like their nest has been blown off of them.
More likely than not, if these bunnies have to be rehabbed out they might die, as they have to be tube fed at that age.
If you have had them for more than a day or two, get them to your local vet who will contact a rehabber or Nature Center to get them help ASAP.
If mom finds them gone and she can't find them, she wont be back. She will think something got them and go off and just have more elsewhere.
regards and good luck!